February 16, 2012

What Color Do Flies Like Best?

Scientists have created a new type of housefly control device that has proven most effective in killing an insect that carries as many as 100 types of germs, researchers from the University of Florida (UFL) announced Wednesday.

Flies have been known to spread diseases such as dysentery, typhoid fever and cholera, and they are often the first pests to occur in abundance when infrastructure is disrupted due to war or natural disasters, such as hurricanes or tsunamis.

The UFL researchers developed the new device after a need for effective fly control came from military personnel battling the persistent pests on the warfront.

The device, known as the Florida Fly-Baiter, is blue rather than the typical yellow fly control devices on the commercial market. The color is the key in controlling the pesky pests, and blue is far more effective than the traditional yellow-colored traps, said Phil Koehler, a professor of urban entomology with UFL´s Institute of Food and Agricultural Sciences.

Koehler and Roberta Pereira, an IFAS associate researcher, worked with two UFL entomology graduates who are also in the Navy to develop the fly control device.

The team found that flies are three times more attracted to the color blue than to yellow, and they further found that yellow actually seemed to repel flies rather than lure them in.

The research was funded by the Department of Defense´s Deployed War-Fighter Protection Program, which sought better ways to protect their troops from insect-spread diseases.

The device works by luring flies with color, smell and other attractants. Once they reach the device, the flies eat poisonous bait that quickly kills them. The device doesn´t trap flies, making it more useful than other traps that need to be replaced often when flies fill up the devices.

Pereira said that more than 40,000 flies were killed with just one application during a recent test of the device. Additional applications of insecticide can be applied as necessary.

Researchers used behavioral tests to determine which color a fly was most likely attracted to. Using electroretinograms to measure the flies´ eye reaction, they found the insects responded more readily to blue.

Adding effectiveness, the trap also includes black stripes covered with insecticide that line the outside. The stripes, tested by Hertz, mimic dark crevices flies like to hide in.

UFL entomology graduate Joseph Diclaro, lead author of the study and device designer, said his time as a US Navy hospital corpsman in Cuba in 1991, when refugees were flooding in, prompted him to make a better fly control device.

“At the time, there were so many displaced people living very closely together, and the garbage and waste accumulated, producing tons of flies,” Diclaro said. “I remember walking out of my tent and just being covered with them.”

The device is effective in controlling house fly, phorid fly, and blow fly problems. It is now available through control distributors. Insecticide for the device is sold separately.

The research results are published in the current issue of the Journal of Medical Entomology.